Field of the Disclosure
The present disclosure, for example, relates to wireless communication systems, and more particularly to techniques for transmitting on multiple carriers of a shared radio frequency spectrum band.
Description of Related Art
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink carriers (e.g., for transmissions from a base station to a UE) and uplink carriers (e.g., for transmissions from a UE to a base station).
Some modes of communication may allow communication between a base station and a UE over a shared radio frequency spectrum band, or over different radio frequency spectrum bands (e.g., a dedicated radio frequency spectrum band and a shared radio frequency spectrum band) of a cellular network. With increasing data traffic in cellular networks that use a dedicated (e.g., licensed) radio frequency spectrum band, offloading of at least some data traffic to a shared (e.g., unlicensed) radio frequency spectrum band may provide a cellular operator with opportunities for enhanced data transmission capacity. A shared radio frequency spectrum band may also provide service in areas where access to a dedicated radio frequency spectrum band is unavailable.
Prior to gaining access to and communicating over a shared radio frequency spectrum band, a base station or UE may perform a listen-before-talk (LBT) procedure to contend for access to one or more carriers of the shared radio frequency spectrum band. When a base station or UE contends for access to multiple carriers of the shared radio frequency spectrum band in parallel, access to some carriers may be won while access to other carriers may be lost. When there are power limitations across one or more subbands of the shared radio frequency spectrum band, and the set of carriers over which the base station or UE transmits varies from one radio frame to another, measurement and demodulation at a receiver can be impacted by the transmitter's use of varying transmit powers, per carrier, from one radio frame to another.